In order that a wheel of motor-vehicle is rotatably supported with respect to a suspension while the rotating speed of this wheel is detected, so that the anti-lock brake system (ABS) or traction control system (TCS) is controlled, the rolling bearing units with the rotating speed detector as shown for example, in the specification of U.S. Pat. No. 4,968,156 are known in the art.
The rolling bearing unit with rotating speed detector mentioned in the above specification is constituted as shown in FIGS. 9 to 10. Specifically, a pair of inner rings 2a, 2b combined by a connection ring 1 are press fitted over a non-rotating axle or shaft 3. And both of the inner rings 2a, 2b are securely clamped between a holder 4 and a nut 5. On the outer peripheral face of each inner ring 2a, 2b, an inner raceway 6 is formed, respectively.
There is a hub 7 that is an outer ring member rotating in use, and outer raceways 8 in double rows are formed on the inner peripheral face of the hub 7.
And, provided between the outer raceways 8 and the inner raceways 6 are a plurality of rolling elements 9, respectively, by which the hub 7 is supported around the axle or shaft 3 freely rotatable.
The vehicle wheel 10 is fixed to a flange 11 provided on the outer peripheral face of this hub 7.
Furthermore, a core metal 13 of the seal ring 12 is internally fitted into the opening portion of the axially inner end of the above hub 7.
The "axially inner" in the specification means the center side in a widthwise direction when installed in the vehicle.
And a tone wheel 14 is fixed in this core metal 13.
This tone wheel 14 is constituted by a permanent magnet, and has S pole and N pole arranged alternatively in a circumferential direction.
A support ring 15 formed by deep-drawing is fitted and fixed on the axially inner end portion of the inner ring 2a which is positioned on the axially inner side than the inner ring 2b.
The seal ring 12 has a seal member 16 the tip portions of which are provided in sliding contact with the inner peripheral face and axially outer face of the support ring 15 in order to prevent the ingress of dust and rainwater into the install section of the rolling elements 9 mentioned above.
And a sensor 17 is supported and fixed in one part of the above support ring 15, and the detecting portion of this sensor 17 is opposed to the axially inner side face of the above tone wheel 14.
A Hall element or a magnetic resistance element is built in this sensor 17, to detect the change of flow directions of magnetic flux corresponding to the change of the magnetic pole of the permanent magnet of the above tone wheel 14, and to change the output of the sensor 17.
In case of the rolling bearing unit with rotating speed detector, the vehicle wheel fixed in the hub 7 can be freely rotatably supported with reference to the axle or shaft 3 which the inner rings 2 are pressed fitted over.
The sensor 17 is opposed to the side of the tone wheel 14 fixed in the hub 7, and as the hub 7 rotates with rotation of the vehicle wheel, the output of the sensor 17 changes.
The frequency at which the output signal of the sensor 17 changes is proportional to the rotating speed of the vehicle wheel. Accordingly, if the output signal of the sensor 17 is input into controllers (not shown), the rotating speed of the vehicle wheel can be obtained to control the ABS and TCS adequately.
In the prior art construction described above, a construction of the so-called active type is adopted, where the tone wheel 14 comprises a magnet the magnetic pole of which changes alternatingly in a circumferential direction, so that magnetic flux sent into the sensor 17 from the rotation side changes actively.
The main portion of the sensor 17 can be composed by the Hall element, magnetic resistance element etc., so that it is possible to make the sensor 17 compact in size keeping enough its output (the output voltage).
However, the high-temperature durability of the Hall element and the magnetic resistance element is not always enough in the art of state, and besides, the price is high.
That is to say, the sensor 17 which is built in the rolling bearing unit with rotating speed detector is exposed to the high-temperature by the frictional heat in the brake actuation. Consequently the enough heat resistance is required for the Hall element and the magnetic resistance element composing this sensor 17.
On the other hand, in the actual situation, the Hall element and the magnetic resistance element often do not exhibit the heat resistance enough. And, the ones which are superior in heat resistance are expensive. Consequently their costs are increased when enough dependability and durability are secured.
The rolling bearing unit with rotating speed detector of this invention will solve the problems mentioned above.